What phase-based billing actually means
Phase-based billing is exactly what it sounds like: instead of billing purely on hours or sending one lump-sum invoice at the end, you bill the client against the distinct phases of the project. The firm and client agree on a fee for SD, another for DD, another for CDs, and so on. As each phase progresses, you invoice a percentage of that phase fee.
Most architecture firms already work this way, even when their software doesn't. The work itself moves through phases, the deliverables map to phases, and clients are used to seeing fee schedules organized that way. Billing the same way is mostly a matter of giving the obvious process a structure.
Why it tends to work well for architecture
The AIA phase structure (SD, DD, CD, Bidding/Negotiation, CA) lines up with how the design itself progresses, so phases are already real checkpoints. They show up in the contract, in the deliverables, in the consultant scopes, and in the client's expectations. Pinning fees and invoices to those checkpoints keeps everything in the same vocabulary.
A few practical upsides:
- The client invoice is easier to defend. Hours-only billing invites “why was this 47 hours?” questions. Phase-based billing turns the conversation into “DD is at 60% complete”, which is much closer to how the client thinks about progress.
- Cash flow becomes more predictable. If you know SD gets billed in two installments and DD in three, you can sketch the year out without a spreadsheet model.
- You can spot a phase going sideways earlier. When the fee is segmented by phase, the budget overrun shows up against one phase, not buried in a project total.
- Additional services slot in cleanly. A phase has a contracted scope. Anything outside it has a clear line to argue from when negotiating the change order.
Where phase-based billing usually breaks down
The model is sensible. The execution is where firms struggle. A few recurring issues:
Picking the fee split in the first place
How much of the total fee goes to SD vs. DD vs. CDs? Front-load too much and CA becomes a slog because you've already burned the fee. Back-load too much and you starve the early design phases of the time they actually need to be good. Most firms eventually settle on a baseline split per project type and adjust from there, but it takes a few projects to get the calibration right.
Estimating percent complete honestly
Phase-based invoicing leans on percent complete. If your time data is thin or stale, percent complete becomes a vibe instead of a number. That's how firms either overbill (and burn client trust later) or underbill (and leave fee on the table they were entitled to).
The mid-project scope swerve
Clients change their mind. Permitting throws something new. Half of CA ends up being something nobody priced. If the fee is locked to phases, every swerve needs to be documented and either absorbed or billed as an AS, in writing, before the work happens. Skip that step and you're eating it.
The consultants
Structural, MEP, civil, and landscape teams all have their own phases that should mirror yours. Reconciling their invoices against your phases, your client invoice, and your contracted pass-through is the part of the month that drains the most patience.
How Archflow approaches it
Archflow's phase and budget tools are built around exactly this workflow. You set up phases (AIA defaults or whatever you customize), allocate fee per phase, and break a phase into tasks if a particular project warrants it. As the team logs hours, budget vs. actual updates against each phase without anyone touching a spreadsheet.
When it's time to bill, invoicing pulls from the phase structure directly. You set the percent complete or invoice off approved hours, and the draft invoice fills itself in. The same applies to consultant pass-through: their invoices come in through the portal against the phases they're on, you approve, and the approved amounts feed the client invoice.
What good firms do
A few habits that separate the firms doing phase billing well:
- Anchor your fee splits in your own history. If your firm has historically spent 18% of the fee in SD on tenant fit-outs, start the next one at 18%, not at “feels right”.
- Make timesheets non-optional. Phase percent complete is only as good as the time data feeding it. Lock periods. Send reminders. The data has to be clean for the rest of this to work.
- Review phases mid-stream, not at handoff. A 30-minute check at the halfway mark of DD will catch the burn problem while you can still do something. A check at the end of DD just tells you what you already lost.
- Write up additional services before doing the work. A short email confirming scope and fee impact, agreed by the client, before any hours go on it. That single habit prevents most of the painful conversations.
- Use a tool that speaks phase. Generic PM tools don't understand fee schedules. You can simulate phase billing in a spreadsheet, but you'll be the one keeping it in sync forever.
If you're still on spreadsheets
Phase-based billing matches how architecture projects work. The reason firms struggle with it is almost always tooling, not concept. If you're still wrangling phase progress in Excel and reconciling it against QuickBooks at the end of the month, book a demo and bring an active project. We'll show you what it looks like when the budget, the time, and the invoice are the same data.